Spatial and frequency-selective optical field coupling absorption in an ultra-thin random metasurface.

Area of Science:

• Nanophotonics and Metasurface Engineering

Background:

• Nanophotonic applications require thin-film structures for spatial and frequency-selective optical field coupling and absorption.
• Achieving high absorption over broad spectral ranges with controlled spatial localization remains a challenge.

Purpose of the Study:

• To demonstrate a simplified thin-film random metasurface for efficient and frequency-selective optical absorption.
• To enable artificial manipulation of spatial coupling and optical absorption through spectral frequency control.

Main Methods:

• Fabrication of a 200-nm-thick random metasurface composed of refractory metal nanoresonators.
• Characterization of optical absorption and field localization across the visible and near-infrared spectrum (0.380-1.167 µm).

Main Results:

• Achieved near-unity absorption (absorptivity > 90%) over the broad spectral range of 0.380-1.167 µm.
• Demonstrated frequency-dependent spatial concentration of the resonant optical field.
• Validated the capability for artificial manipulation of spatial coupling and optical absorption via spectral frequency.

Conclusions:

• The developed random metasurface offers a simplified approach to achieving broadband, high optical absorption.
• The frequency-selective spatial field localization provides a pathway for advanced optical field manipulation.
• The methods are broadly applicable for frequency-selective nanoscale optical field control across a wide energy range.